The demand for wireless network access and performance has been constantly increasing due in part to the increased popularity of wireless devices. Moreover, as wireless device functionality has increased, so has the quality and performance requirements for wireless data. For example, data intensive video streaming to a mobile device typically involves high quality service requirements such that the user experience is not negatively affected. The result is that wireless data traffic has been increasing almost exponentially while circuit switched traffic has been increasing at a slower pace. While protocols such as long term evolution (LTE) provide higher bandwidth, there is a need to support an increasing number of devices which, in turn, have higher bandwidth requirements.
Wireless network operators have addressed the increased demand for wireless network access and performance in several ways. Some wireless network operators have deployed hierarchical cell structures such as those found in heterogeneous network deployments in order to increase wireless access and performance. Heterogeneous network deployments are configured such that a macro cell coverage area includes one or more pico cells in which the mobile device communicates with the macro cell and/or pico cell(s). For example, wireless network operators can place pico cells at “hot spots” to service specific areas within the macro cell coverage area that typically have a high number of mobile devices.
There are several configurations for heterogeneous deployments including a multi-cell identification (ID) approach and a shared cell ID approach. The multi-cell ID approach includes assigning different cell IDs to each macro cell and pico cell such that each cell is required to transmit different sync, broadcast and mobile device specific control channels. However, a dense deployment of pico cells within a macro cell substantially increases signaling due to frequency handovers for users moving at high speeds.
The shared cell ID approach to heterogeneous networks includes assigning the same cell ID to the macro cell and each pico cell within a macro cell coverage area. The shared cell approach simplifies signaling from the mobile device perspective as the mobile device does not distinguish the macro cell from the pico cell, i.e., the mobile device only “sees” one cell ID while traveling within the macro cell coverage area. Also, the need for additional control signaling overhead associated with hand-offs within the macro cell coverage region is avoided as the mobile device moves between pico cells. The shared cell ID approach also avoids proliferation of cell IDs that occurs in the multi-cell ID approach.
However, the shared cell ID approach is not without faults. For example, a receiver at the macro cell may receive mobile device traffic forwarded from each pico cell. Processing the received traffic can require a substantial amount of resources. For example, the receiver at a macro cell treats the shared cells as a distributed antenna system in which all the link signals of UEs received from the pico cells are summed without regard to the properties of each uplink signal. While data volume scales linearly with each additional uplink signal that is being processed, processing for antenna combining requires a computational complexity that grows exponentially with the number of antennas or received uplink signals. In other words, processing additional uplink signals for antenna combining can rapidly become an issue for limited computational resources. Also, processing all uplink signals received from the pico cells adds noise to the overall received signal, which in turn reduces data throughput. Therefore, current macro cell receivers are unable to take advantage of the different signal information provided by the shared cell approach.